[1] Keenan, a prolific theater actor, appeared in more than 100 stage productions throughout his career, including shows at the San Diego Shakespeare Festival, Seattle Repertory Theatre, the Mark Taper Forum, the Ahmanson Theatre, and the South Coast Repertory.

[1] Notably, he starred in the Peter Hall's Broadway revival of Amadeus, where he portrayed Baron van Swieten, from 1999 to 2000.

Keenan also successfully taught at The American Academy of Dramatic Arts-at their Los Angeles Campus.

Beginning in 1987, Keenan directed at least one play or other stage production for the USC School of Dramatic Arts until his retirement in 2015.

[1] Michael Keenan died from natural causes at the Motion Picture & Television Country House and Hospital (MPTF) in the Woodland Hills neighborhood of Los Angeles on April 30, 2020, at the age of 80.